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• ffmpeg - color-grading video material AND display original source as picture-in-picture, using -filter_complex

  5 octobre 2019, par raven

  this is my first post on this forum, so please be gentle in case I accidentally do trip over any forum rules that I would not know of yet :).

  I would like to apply some color-grading to underwater GoPro footage. To quicker gauge the effect of my color settings (trial-and-error, as of yet), would like to see the original input video stream as a PIP (e.g., scaled down to 50% or even 30%), in the bottom-right corner of the converted output movie.

  I have one input movie that is going to be color graded. The PIP should use the original as an input, just a scaled-down version of it.

  I would like to use ffmpeg’s "-filter_complex" option to do the PIP, but all examples I can find on "-filter_complex" would use two already existing movies. Instead, I would like to make the color-corrected stream an on-the-fly input to "-filter_complex", which then renders the PIP.

  Is that doable, all in one go ?

  Both the individual snippets below work fine, I now would like to combine these and skip the creation of an intermediate color-graded TMP output which then gets combined, with the original, in a final PIP creation process.
  Your help combining these two separate steps into one single "-filter_complex" action is greatly appreciated !

  Thanks in advance,
  raven.

  [existing code snippets (M$ batch files)]
  
  
  
  ::declarations/defines::
  
  set "INPUT="
  
  set "TMP="
  
  set "OUTPUT="
  
  set "FFMPG="
  
  set "QU=9" :: quality settings
  
  
  
  set "CONV='"0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 
  
  0 -1 0:0 -1 0 -1 5 -1 0 -1 0'"" :: sharpening convolution filter
  
  
  
  ::color-grading part::
  
  %FFMPG% -i %INPUT% -vf convolution=%CONV%,colorbalance=rs=%rs%:gs=%gs%:bs=%bs%:rm=%rm%:gm=%gm%:bm=%bm%:rh=%rh%:gh=%gh%:bh=%bh% -q:v %QU% -codec:v mpeg4 %TMP%
  
  
  
  ::PIP part::
  
  %FFMPG% -i %TMP% -i %INPUT% -filter_complex "[1]scale=iw/3:ih/3 
  
  [pip]; [0][pip] overlay=main_w-overlay_w-10:main_h-overlay_h-10" -q:v 
  
  %QU% -codec:v mpeg4 %OUTPUT%
  
  
  
  [/existing code]

• `sage -pip install —user ffmpeg` did not make the "`OSError : Error : ffmpeg does not appear to be installed.`" message go away

  2 septembre 2019, par SomeoneElse

  I am running a Docker instance of Cocalc on a Ubuntu 16 server. Everything seems to be working but I am trying to debug why sage -pip install --user ffmpeg did not make the "OSError: Error: ffmpeg does not appear to be installed." message go away, even though it said it had been installed. Here is the full message.

  Error in lines 9-9
  
  Traceback (most recent call last):
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 1188, in execute
  
      flags=compile_flags) in namespace, locals
  
    File "", line 1, in <module>
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2944, in show
  
      s = show0(objs, combine_all=True)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2903, in show0
  
      b = show0(a)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2868, in show0
  
      show_animation(obj, **kwds)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2642, in show_animation
  
      obj.ffmpeg(t, delay=delay, **kwds)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/animate.py", line 885, in ffmpeg
  
      raise OSError(msg)
  
  OSError: Error: ffmpeg does not appear to be installed. Saving an animation to
  
  a movie file in any format other than GIF requires this software, so
  
  please install it and try again.
  
  </module>

  For reference, here is the code that gives the error :

  n = var("n")
  
  frames = []
  
  xr = (x, 0, 1)
  
  for k in srange(1, 50):
  
      g = plot((sum((-1)^(n-1)*sin(n*x)/n,n,1,k)), xr, color="blue", legend_label='k = %d' % k)
  
      g += plot(x/2, xr, color="green", legend_label="x/2")
  
      frames.append(g)
  
  
  
  a = animate(frames, ymin=0.0, ymax=1.0, legend_loc=(0.2,0.8))
  
  a.show()

• How to create a 720x480 blank mpg

  6 août 2019, par wckai

  In order to join some video clip(720x480 [SAR 8:9 DAR 4:3]) and leave two seconds blank gap between each one, i try to make an blank clip by code

  ffmpeg -t 2 -s 720x480 -f rawvideo -pix_fmt rgb24 -r 29.97 -i /dev/zero -f lavfi -i anullsrc -shortest empty_720x480.mpg

  but when i try to concat clips,

  -filter_complex "[0:v:0]setsar=8/9[v0];[1:v:0][1:a:0][v0][0:a:0][2:v:0][2:a:0][v0][0:a:0][3:v:0][3:a:0]concat=n=5:v=1:a=1[outv][outa]"

  an error occurs

  Input link in3:v0 parameters (size 720x480, SAR 1:1) do not match the corresponding output link in0:v0 parameters (720x480, SAR 8:9)

  I have try create an 720x540 first and scale to 720x480(), but still not the same with 720x480 [SAR 200:219 DAR 100:73].

  I have no idel how to solve it, please help.